Chapter 6 - Tropospheric Biennial Oscillation of the Western Pacific Subtropical High and Its Relationships With the Tropical Sea Surface Temperature and Atmospheric Circulation Anomalies

Abstract

There is a significant period of tropospheric biennial oscillation (TBO) over the Asian monsoon region at the interannual timescales, which has important influences on monsoon climate anomalies. The TBO component of the western Pacific subtropical high (WPSH), which is one of the dominant members of the East Asian summer monsoon system, and its relationships with the tropical sea surface temperature (SST) and atmospheric circulation anomalies were examined in this chapter. It is found that the TBO component of the WPSH had an obvious transition in the late-1970s, with stronger amplitudes of the TBO variability after this period. The time-lag correlations between the WPSH’s TBO and tropical SST anomalies are more significant and have longer correlation duration than that between the raw data. In the course of the WPSH’s TBO cycle, the occurrence of the El Niño (La Niña)-like anomaly in winter is always coupled with the weak (strong) East Asian winter monsoon, with the most significant enhancing (weakening) phase of the WPSH’s TBO. The distribution of the tropical SST and atmospheric circulation anomalies are asymmetric in the TBO cycle. The WPSH’s TBO is more significant in the El Niño-like developing phase than in the La Niña-like developing phase. Therefore during the El Niño-like developing phase, the TBO signal should be paid more attention for short-term climate prediction.